When it comes to precision medicine, commonly known as personalized medicine, COVID-19 and cancer tend to grab the headlines. Yet there are other diseases where this field is also being applied, including autoimmune diseases such as rheumatoid arthritis (RA). RA is characterized by long-standing inflammation of joints that causes progressive joint damage and leads to deformity, disability, and eventual death. Prediction of RA risk entails analysis of gene–environment interactions, measurement of cytokines, and detection of autoantibodies. Both arms of the immune system, the innate and adaptive, are involved in its pathogenesis. As shown in this supplement—comprising three research articles and two abstracts—scientists are decoding the cell signaling that occurs between the innate and adaptive arms of the immune system. Much progress has been made, with new therapies becoming more of a possibility.